Technical Abstract:
One hundred ninety-nine crossbred beef heifer calves (205 ± 7.9 kg initial BW) were used in a 44-d receiving trial with 2 dietary treatments (9 pens/treatment) in a completely randomized design. Heifers were weighed and bled on d 0, 16, 30, and 44 after arrival. Blood was collected by jugular venipuncture, and serum was analyzed for cortisol, several cytokines, and 2 acute-phase proteins. Exit velocity was recorded by an electronic infrared timer system each time heifers were weighed. Animals were brought to the processing facility in pen groups of 10 to 12, and no effort was made to control processing sequence of individual animals. Exit velocity was not related (P = 0.71) to processing sequence. Repeatability of exit velocity was 77%. A trend was evident for a negative linear relationship between average exit velocity and 44-d ADG (P = 0.08) and for positive linear relationships between exit velocity and serum cortisol (P = 0.10) and interferon-gamma concentrations (P = 0.13). At d 44, the heifers were transported to a commercial feedlot, fed for 200 d, and individual carcass data were collected at slaughter. After controlling for treatment and pen effects, exit velocity, averaged over the 4 measurement times, was not related to carcass characteristics (P > 0.23) nor to ADG over the entire 240-d trial (P = 0.92). Although exit velocity measured during the receiving period seemed to be associated with increased serum cortisol and decreased ADG during the receiving period, it was not associated with ADG or carcass measurements after an extended feeding period. Thus, further research is needed to determine whether extended feeding periods during which cattle are not handled might mitigate deleterious effects of exit velocity on cattle performance.